1. Field of the Invention
The present invention relates to a nonreciprocal circuit device, for example, an isolator, used in a high-frequency band such as a microwave band, and further to a communication apparatus using this nonreciprocal circuit device.
2. Description of the Related Art
Hitherto, a conventional lumped-constant type circulator has been formed by accommodating, in a case, a plurality of centeral conductors which is disposed adjacent to a ferrite plate so as to intersect each other, and a magnet for applying a DC magnetic field to a ferrite plate. On the other hand, the isolator has been formed by terminating a predetermined port among three ports, by a resistor.
FIGS. 10A and 10B are bottom views showing two types of conventional isolators. Here, a lower yoke 8 doubling as a lower case, a resin case 7, an input terminal In, an output terminal Out, and a ground terminal Gnd are shown.
As shown in FIG. 10, in a conventional isolator, both of the input terminal and output terminal have been disposed along one side in the longitudinal or transverse direction, of the resin case 7. As a result, the directivity of the input/output of the isolator has been determined in advance. Hence, when attempting to reverse the positional relation of the signal input and signal output in the case where the isolator has been mounted on a circuit board of electronic equipment such as a communication apparatus, it has been necessary to replace this isolator with an isolator which is opposite thereto in the nonreciprocal characteristics of input/output. Of course, the nonreciprocal characteristics of input/output can be reversed by reversing the polarity of a DC magnetic field which is applied to the ferrite plate. However, it is very difficult and quite unrealistic that users reverse the polarity of the magnet and performs adjustment of the characteristics of the isolator.
On the other hand, the manufacturer of the isolators is required to prepare beforehand for two types of isolators which differ in the direction of input/output from each other, in order to meet the request from users. This causes an increase in the cost of production and management.
Accordingly, it is an object of the present invention to solve the above-described problems, and to provide a nonreciprocal circuit device which allows the relationship between the input and the output to be reversed using the identical terminal layout on a mounting substrate, only by preparing for a single type of nonreciprocal circuit device, and further to provide a communication apparatus using this nonreciprocal circuit device.
In accordance with the present invention, there is provided a nonreciprocal circuit device comprising a magnetic body on which a DC magnetic field is applied, and a centeral conductor disposed adjacent to the magnetic body. In this nonreciprocal circuit device, input/output terminals connected to the centeral conductor are disposed at substantially rotation-symmetrical positions with respect to substantially the central portion of the bottom surface of the nonreciprocal circuit device.
The described features allow the direction of nonreciprocal characteristics of input/output to be reversed only by rotating the nonreciprocal circuit device by substantially 180xc2x0 along the plane of the bottom thereof. Therefore, only by preparing for a single type of nonreciprocal circuit device, the directivity of input/output can be determined when the nonreciprocal circuit device is mounted on a circuit board of electronic equipment such as a communication apparatus.
In the present invention, it is preferable that a plurality of ground terminals connected to the centeral conductor be provided, and that the ground terminals be disposed at substantially rotation-symmetrical positions with respect to the substantially central portion of the bottom surface of the nonreciprocal circuit device. These features allow the ground connection between the ground terminals of the nonreciprocal circuit device and the ground electrodes on the mounting substrate to be established with a reliability, irrespective of the mounting state of the nonreciprocal circuit device on a mounting substrate.
The present invention further provides a communication apparatus including above-described nonreciprocal circuit device.
The above and other objects, features, and advantages of the present invention will be clear from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings.